Insulator structure for electrostatic condensers and the like



Dec. 29, 1925 1,567,544

v I. P. RODMAN INSULATOR STRUCTURE FOR ELECTROSTATIC CONDENSERS I AND THE LIKE Filed March 8, 1924 INVENTOR [SaacPRodman ATTORNEYS BY f Patented Dec. 29, 1925.

UNITED STATES PATENT OFFICE.

ISAAC P. ROIDMAN, OF NEWARK, NEW JERSEY, ASSIGNOR TO GAROD CORPORATION, OF NEWARK. NEW JERSEY, A CORPORATION OF NEW JERSEY.

INSULATOR STRUCTURE FOR ELECTROSTATIC CONDENSERS AND THE LIKE.

Application filed March 8, 1924. Serial No. 697,725..

To all whom it may concern:

Be it known that I. ISAAC P. RonMAN, a

' citizen of the United States,'residing at Newark, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Insulator Structures for Electrostatic Condensers and the like; and I do hereby declare the following to be a full, -clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention has to do with means for effecting improved insulation, and relates, more specifically to the construction of electrostatic condensers.

The object of this invention is to provide simple and relatively inexpensive means for effecting extraordinarily high insulation and particularly to provide a structure of th 1s kind which may be used to advantage in electrostatic condensers. More specifically, the object of the invention is to provide a variable electrostatic condenser having greatly increased insulation between the two sets of plates and correspondingly greatly reduced losses as compared with the corresponding characteristics of condensers heretofore commonly used.

I have found that-in radio practice, and especially radio reception, the losses ar sing from poor and only moderately good 1nsu-, lation between the fixed and rotatable plates of the variable condensers is a much more important factor than has heretofore been generally recognized. The present invention provides a condenser structure of relatively simple design in which the insulation resistance is exceedingly high and in which the losses due to leakage are practically nil.

The present invention is an improvement on the structure disclosed and claimed in my copending application Serial No. 655,819, filed August 6, 1923. In that copending application the fixed plates are adjustably mounted on rods of dielectric material such disturbed by expansion and contraction of the condenser structure due to variations.

Although the insulation resistance between the fixed and variable plates in the condenser structure described in the abovementioned copending application is very high, it has been found that a still further improvement could be effected by mounting the supportingrods on pointed set screws or equivalent supporting elements. Bythis provision the contacts between the dielectric supporting rods and the framework of the condenser structure is reduced to a minimum and the possibility of surface leakage is correspondingly reduced.

One of the most important advantages of this invention arises from the fact that the supporting rods for the fixed plates may be temperature 7 made of .a dielectric material of relatively poor insulating qualities as compared, forinstance, with that of glass, but which possesses other physical characteristics rendering its use more desirable. For example, it is possible by virtue of this invention to employ supporting rods made of hard rubber or bakelite or other compositions which are a great deal less brittle than glass and yet retain substantially the same hlgh insulation characteristics as could be realized with glass rods in the structure of my copending application. In those cases where the maximum insulation is desired and there is no objection to the sacrifice of physical strength involved, the present inventlon may be incorporated in a condenser structure in which the supporting rods are made of glass.

The field of usefulness of the improved insulating structure accordin to this invention is not by any means limlted to electrostatic condensers. Insulator structures coming within the scope of this invention may be used to advantage in many cases where it is desired to insure extremely high insulatio' In the accompanying drawin "Figs. 1 to 4 inclusive ill'ustratein plan' e evation and cross section a variable condenser structure in accordance with the preferred embodiment of the invention. A

Fig. 1 is a plan view;

lustrating an alternative arrangement for n the clamping supporting and centering the rods.

The condenser comprises a group of parallel rotatable plates 1 which are mounted on a shaft 2 and rotatable therewith. A group of parallel fixed plates 3 are each secured together by means of bolts 4 and mounted in proper spaced relation with respect to the rotatable plates 1. The fixed plates are attached by means of three clamping lugs 5.

to three supporting rods 6, which may be made of any suitable insulating material such as glass, hard rubber, bakelite, or other dielectric compositions. The two ends of each of the rods 6 are preferably countersunk, as shown in Fig. 4, or counterbored, as shown in Fig. 5, to provide seats for the pointed centering and supporting elements 7 and 8. The element 7 may be a headless pointed set screw, as shown, or any other equivalent device. The element 8 is preferably in the form of a set screw, as shown, and is preferably provided with a lock nut 9. The cast frame members 10 and 11 are preferably provided with recesses 10 and 11, into which the supporting rods 6 project. These recesses. as shown in Fig. 4,

should be of sufliciently larger diameter than that of the supporting rods so that there is a clearance all around as shown. The counter-sunk recesses in the ends of the rods 6 are preferably of a slightly larger angle than that of the points of the centering elements 7 and 8, so that the contacts between the rods and the centering elements is reduced asfar as practicable to a mere point contact. Although it is technically preferable that the 4 ends of the supporting rods 6 be countersunk as shown in Fig. 4, it is found that for most purposes the arrangement of Fig. 5, wherein the ends of the rods are counterbored instead of countersunk, is substantially as satisfactory, providing the diameter of the counterbores is relatively small so that the lines of contact between the rods and the supporting elements are short. It is not at all essential to the object sought that the ends of the rods be either countersunk or counterbored. The centering ele-' ments 7 and 8 may, for instance, engage the fiat end surfaces of the supporting rods if the recesses are not provided. It is obvious that still further equivalent arrangements can be readily devised. The clamping lugs 5 are each provided with a machine screw 12 by means of which the lugs may be caused to grip the supporting rods. When lugs are loosened, the fixed plate assembly may be moved along the sup porting rods for the purpose of adjusting the spacing between the two sets of plates.

The two frame members 10 and 11 are secured together in proper spaced relation by means of three shouldered studs 13 which are provided with cap nuts 14..

The remaining details of the structure illustrated are quite apparent from the drawing, and since they form no part of the present invention, it is thought unnecessary to describe them in detail.

The invention is not limited to variable condensers, as it is equally applicable to fixed condensers of any of the types in which the dielectric between the plates is not of solid form, as, for instance, air and oil condensers. Furthermore, the invention as applied to either a fixed or variable condenser is capable of considerable modification within its spirit and scope.

I claim:

1. An electrostatic condenser comprising a plurality of sets of plates disposed in spaced relation one to another. at least one of said sets of plates being supported ona support of dielectric material, and supporting elements in contact with two ends of said support, the contact areas between said supports and said supporting elements being very small. n.

2. An electrostatic condenser comprising a plurality of sets of plates disposed in spaced relation one to another, at least one of said sets of plates being supported on a rod of dielectric material, supporting elements for engaging the two ends of said rod, the engagement between said rod and said supporting elements being of point contact form. p e

3. An electrostatic condenser comprising a plurality of sets of plates disposed in spaced relation one to another, a rod of dielectricmaterial, at least one of said sets of plates being supported on said rod, the two ends of said rod being countersunk, pointed ill) supporting elements for engaging the countersunk ends of'said rod respectively, said supporting elements being adapted to support said rod.

4. An electrostatic condenser comprising a plurality of sets of plates disposed in spaced relation one to another, a plurality of rods of dielectric material for supporting one of said sets of plates, means for securing said last-mentioned set of plates to said rods, each end of each of said rods being provided with a countersunk recess, and pointed centering elements each engaging through the medium of its point the end of one of said rods, said points being seated in said countersunk recesses.

5. An electrostatic condenser comprising a plurality of sets of plates disposed in spaced relation one to another, a plurality of rods of dielectric material for supporting one of said sets of plates, means for clampingly securing said last-mentioned set of plates to said rods, a pair of frame members each having recesses into which the 7 ends of said rods project, each end of each of said rods being provided with a conical countersunk recess, and pointed centering elements each attached to one of said frame L members, said centering elements having their points seated in said conical recesses 10 respectively. a In testimony wherebfI aflix my signature.

ISAAC P. RODMAN. 

